The present invention relates to the field of devices to study the electrophysiology of nerve and muscle tissues, and in particular to a dynamically configurable clamp device used to measure and control nerve and muscle tissues.
A neuroscience laboratory is generally equipped with at least one voltage clamp system to study the electrophysiology of nerve and muscle tissues. Current-voltage relations across excitable membranes are time varying, nonlinear, and spatially distributive. By clamping the membrane potential to a step function, the voltage clamp system momentarily achieves spatial coherence and voltage invariance. The current injected back into the cell for maintaining a constant membrane potential can be equated to the ionic current that induces an action potential. Further decomposition of the ionic current due to sodium, potassium, and calcium can be done by ionic substitutions in the bathing solution of the tissue.
Half a century ago Cole (Cole, K. S., Dynamic electrical characteristics of the squid axon membrane, Arch. Sci. Physiol. 3, 253-258) introduced the voltage clamp technique, which lead to the landmark study of axonal current-voltage relations by Hodgkin, Huxley, and Katz in 1952 (Hodgkin, A. L., and Huxley A. F., Currents Carried by Sodium and Potassium Ions through the Membrane of the Giant Axon of Lologo, J. Physiol. Lond. 116, 449-472, 1952; Hodgkin, A. L., and Huxley A. F., A Quantitative Description of Membrane Current and its Application to Conduction and Excitation in the Nerve, J. Physiol. Lond. 116, 500-544, 1952; Hodgkin, A. L., Huxley A. F. and Katz B., Measurement of Current-Voltage Relations in the Membrane of the Giant Axon of Loligo, J. Physiol. Lond. 116, 424-448, 1952). Hodgkin and Huxley were awarded the Nobel Prize for their contributions in neuroscience. The voltage clamp is arguably the most useful technique for studying membrane excitation to date.
The dynamic clamp developed by Robinson (Robinson, H. P., and Kawai, N., Injection of Digitally Synthesized Synaptic Conductance Transients to Measure the Integrative Properties of Neurons, J. Neurosci. Methods 49, 157-165, 1993; Robinson, H. P., Conductance Injection-Letter to the Editor, with Reply by Sharp, A. A., O'Neil M. B., Abbott, L. F., and Marder, E., Trends in Neurosci. 17, 147-148 1994) and Sharp et al. (Sharp, A. A., O'Neil, M. B., Abbott, L. F., and Marder E., Dynamic Clamp: Computer-Generated Conductances in Real Neurons, J. Neurophysiol. 69, 992-995, 1993; Sharp, A. A., O'Neil, M. B., Abbott, L. F., and Marder E., The Dynamic Clamp: Artificial Conductances in Biological Neurons. Trends in Neurosci. 16, 389-394, 1993) has been used to create an artificial synapse by measuring voltage in one neuron and injecting current into another neuron. Their instruments were based on the traditional voltage clamp-amplifier coupled with a PC data acquisition system. Such a system does not provide sufficient speed and flexibility to be a general instrument for neuroscience research.
Current clamps are also known. However, prior art voltage, current and dynamic clamps have been dedicated, non-configurable devices that perform only their respective voltage, current or dynamic clamp functions, respectively. That is, prior art voltage clamps would only operate as a voltage clamp, and could not be reconfigured to operate as a dynamic clamp, and visa versa.
Therefore, there is a need for a system that can automatically be configured to operate in a desired clamp mode in response to a user command.